1. Field of the Invention
The present invention relates to a valve timing control apparatus for an internal combustion engine.
2. Description of the Related Art
A valve timing control apparatus disclosed in JP 6-159105 A is an example of a conventional valve timing control apparatus. This is a device in which a control amount of a predetermined operating state of an oil pressure regulating valve as one valve timing changing means, is learned, and then a drive signal is corrected in accordance with the learned control amount.
The structure of the conventional valve timing control apparatus discussed in JP 6-159105 A is shown in FIG. 7. In the figure, reference numeral 701 denotes a relative rotation angle detecting means, reference numeral 702 denotes a target relative rotation angle calculating means, reference numeral 703 denotes a controlling means, reference numeral 704 denotes a learning means, reference numeral 705 denotes a driving means, and reference numeral 706 denotes a valve timing regulating means.
An operation thereof will be explained. The relative rotational angle between crank angle and cam angle, that is the valve timing, is detected in the relative rotation angle detecting means 701. The target relative rotation angle corresponding to an engine operation state is calculated in the target relative rotation angle calculating means 702. A control amount for performing feedback control by the variation between the target relative rotational angle and the detected relative rotational angle is calculated by the controlling means 703. The control amount is calculated in which a feedback control is performed in accordance with a deviation between the target relative rotational angle and the detected relative rotational angle by the controlling means 703. The learning means 704 learns the control amount in a holding state of the controlling means 703, in which the deviation between the target relative rotational angle and the detected relative rotational angle falls within a predetermined range. The controlling means 703 calculates a control amount, based on the value learned by the learning means 704, during control amount calculation. The driving means 705 drives the valve timing regulating means 706 in accordance with the control amount calculated by the controlling means 703.
The feedback control is thus performed by using the deviation between the target relative rotational angle and the detected relative rotational angle in the conventional valve timing control apparatus. Further, the control amount in a state in which the target relative rotational angle and the detected relative rotational angle are nearly identical is learned, and the control amount is calculated based on the learn value. A variation in components such as oil pressure regulating valves is therefore compensated for, and controllability is ensured. However, compensation is not performed with respect to detection defects in the crank angle and the cam angle due to superposition of noises, detection slippage, and the like in a crank angle sensor and a cam angle sensor. Problems thus exist in that cylinder identification irregularities develop, and this invites shocks, increased exhaust gas, and the like.
The present invention has been made in order to resolve these problems, and an object of the present invention is to obtain a valve timing control apparatus for an internal combustion engine which controls valve timing and prevents shocks and increased exhaust gas, even for cases in which cylinder identification irregularities develop.
According to the present invention, there is provided a valve timing control apparatus for an internal combustion engine, including: a crank angle detecting means for detecting a crank angle; a cam angle detecting means for detecting a cam angle; a valve timing changing means for changing a relative position of a cam shaft and a crank shaft at least for an intake or an exhaust; a cylinder identifying means for performing cylinder identification based on detected results by the crank angle detecting means and the cam angle detecting means; a valve timing detecting means for detecting valve timing based on the detected results by the crank angle detecting means and the cam angle detecting means; and a valve timing controlling means for controlling the valve timing changing means based on a value detected by the valve timing detecting means, in which the valve timing controlling means performs control at a neutral point when cylinder identification by the cylinder identifying means is in an indefinite state.